Gas turbine engine

ABSTRACT

A method of manufacturing a part comprises providing a component for cutting and directing a water jet at the component so as to cut the component. The water jet comprises water and abrasive particles having a nucleus made from a first substance and a second substance surrounding the nucleus, the first substance being denser than the second substance.

CROSS-REFERENCE TO RELATED APPLICATIONS

This specification is based upon and claims the benefit of priority fromUK Patent Application Number 1712479.3 filed on 3 Aug. 2017, the entirecontents of which are incorporated herein by reference.

BACKGROUND Technical Field

The present disclosure concerns a method of manufacture and/or a methodof water jet cutting.

Description of the Related Art

Gas turbine engines are typically employed to power aircraft. Typicallya gas turbine engine will comprise an axial fan driven by an enginecore. The engine core is generally made up of one or more turbines whichdrive respective compressors via coaxial shafts. The fan is usuallydriven off an additional lower pressure turbine in the engine core.

The fan includes a plurality of blades arranged around a hub. The bladesmay be metallic or composite blades. Composite blades generally includea body made from a carbon reinforced plastic matrix which may bereinforced in various ways. A metallic leading edge, and often ametallic trailing edge is provided on the body.

The metallic leading edge can be manufactured in a number of differentways, and in some examples the metallic leading edges need to be cutduring the manufacturing process. This cutting can be done using waterjet cutting. Water on its own is not sufficiently abrasive to cut themetal, so abrasive garnet particles are added to the water. However, thegarnet can become embedded in the metal work contaminating the surfaceof the cut component. Garnet is chemically inert, so it is not readilyremoved using chemical processes and as such mechanical processes needto be employed to remove the embedded particles. Removal of the garnetparticles from the surface of the component adds cost and time to themanufacturing process.

SUMMARY

According to an aspect there is provided a method of manufacturing apart, the method comprising providing a component for cutting anddirecting a water jet at the component so as to cut the component. Thewater jet comprises water and abrasive particles having a nucleus madefrom a first substance and a second substance surrounding the nucleus.The first substance may be denser than the second substance. The secondsubstance may be a liquid at atmospheric temperature and pressure. Thefirst substance may be solid at atmospheric temperature and pressure.The second substance may be a frozen liquid, e.g. the second substancemay be ice. Ice refers to frozen water. Frozen water consistsessentially of H₂O and any impurities. In alternative examples, thesecond substance may be an alternative frozen liquid.

The nucleus may comprise carbon. The nucleus may consist of or consistessentially of carbon or carbon fibre. The nucleus may comprise one ormore carbon fibres or particles.

The nucleus may be defined by a single carbon fibre.

The nucleus may comprise acrylic. The acrylic nucleus may be 3D printedprior to being surrounded by the second substance.

The part may be a fan blade for a gas turbine engine, e.g. the componentonce cut may be a metal leading edge or trailing edge of a fan blade.

According to an aspect there is provided a method of water jet cutting acomponent, the method comprising providing a component for cutting anddirecting a water jet at the component so as to cut the component. Thewater jet comprises water and abrasive particles having a nucleus madefrom a first substance and a second substance surrounding the nucleus,the second substance being different to the first substance.

The method may comprise one or more features of the previous aspect.

According to an aspect there is provided a method of manufacturing apart, the method comprising providing a component for cutting anddirecting a water jet at the component so as to cut the component, thewater jet comprising water and carbon particles.

The method may comprise one or more features of the previous aspect.

According to an aspect there is provided a method of water jet cuttingcomprising providing a component for cutting, and directing a water jetat the component so as to cut the component. The water jet compriseswater and carbon particles.

The carbon particles may be surrounded in a substance that is liquid atatmospheric temperature and pressure. For example, the carbon particlesmay be surrounded by ice.

The method may comprise one or more features of the previous aspect.

The skilled person will appreciate that except where mutually exclusive,a feature described in relation to any one of the above aspects may beapplied mutatis mutandis to any other aspect. Furthermore except wheremutually exclusive any feature described herein may be applied to anyaspect and/or combined with any other feature described herein.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments will now be described by way of example only, with referenceto the Figures, in which:

FIG. 1 is a sectional side view of a gas turbine engine;

FIG. 2 is a schematic of a water jet cutting arrangement and component;

FIG. 3 illustrates water with particles suspended in it for use as awater jet;

FIG. 4 is a schematic of a feed of particles into a water jet;

FIG. 5 is a schematic of equipment used to make the particlesillustrated in FIG. 3; and

FIG. 6 is a schematic of equipment used to grow abrasive particles

DETAILED DESCRIPTION

With reference to FIG. 1, a gas turbine engine is generally indicated at10, having a principal and rotational axis 11. The engine 10 comprises,in axial flow series, an air intake 12, a propulsive fan 13, anintermediate pressure compressor 14, a high-pressure compressor 15,combustion equipment 16, a high-pressure turbine 17, an intermediatepressure turbine 18, a low-pressure turbine 19 and an exhaust nozzle 20.A nacelle 21 generally surrounds the engine 10 and defines both theintake 12 and the exhaust nozzle 20.

The gas turbine engine 10 works in the conventional manner so that airentering the intake 12 is accelerated by the fan 13 to produce two airflows: a first air flow into the intermediate pressure compressor 14 anda second air flow which passes through a bypass duct 22 to providepropulsive thrust. The intermediate pressure compressor 14 compressesthe air flow directed into it before delivering that air to the highpressure compressor 15 where further compression takes place.

The compressed air exhausted from the high-pressure compressor 15 isdirected into the combustion equipment 16 where it is mixed with fueland the mixture combusted. The resultant hot combustion products thenexpand through, and thereby drive the high, intermediate andlow-pressure turbines 17, 18, 19 before being exhausted through thenozzle 20 to provide additional propulsive thrust. The high 17,intermediate 18 and low 19 pressure turbines drive respectively the highpressure compressor 15, intermediate pressure compressor 14 and fan 13,each by suitable interconnecting shaft.

Other gas turbine engines to which the present disclosure may be appliedmay have alternative configurations. By way of example such engines mayhave an alternative number of interconnecting shafts (e.g. two) and/oran alternative number of compressors and/or turbines. Further the enginemay comprise a gearbox provided in the drive train from a turbine to acompressor and/or fan.

The fan 13 includes a plurality of fan blades 24 arranged around a hub.In the present example, the fan blades are composite fan blades andinclude a metallic leading edge 25. The metallic leading edge is madefrom metal and is at least partially cut to size using water jetcutting.

The method of water jet cutting will now be described in more detail.Referring to FIG. 2, to cut a component 26 a water jet 28 is directed atthe component. The water jet is delivered from cutting equipment 30.

Referring to FIG. 3, the water jet includes water 32 and abrasiveparticles 34. The abrasive particles include a nucleus 36 of a firstsubstance. The nucleus is surrounded by a second substance 38. In thepresent example, the nucleus is made from carbon, more specifically inthis example carbon fibre. The second substance in this example is ice,i.e. frozen water.

The carbon fibre is defined by short sharp lengths of carbon. These canbe produced with a high aspect ratio. The carbon fibres can be boughtoff the shelf or may be manufactured from carbon rod stock. Tomanufacture the carbon fibres, conventional methods can be used such asa using a slotted cutting wheel or shearing jaws.

Referring now to FIG. 4, the cutting equipment 30 includes a hopper 40for receiving solid particles (e.g. carbon fibre nuclei surrounded byice). The equipment also includes a high pressure supply 42A, 42B ofwater. A water outlet 44 is provided through which the high pressuresupply of water can flow. A focus tube 46 projects into the outlet fromthe hopper 40, such that a flow of solid particles from the hopper canmix with the water. A control orifice 48 is provided at the exit of thewater outlet, so as to control the flow of water and solid particles.

To cut a component, solid particles are supplied to the hopper 40,either continuously or in batches. High pressure water is suppliedthrough the inlets 42A, 42B. This water then flows to the water outlet44. Simultaneously, particles are released from the hopper into thewater in the outlet. The orifice 48 then funnels the water and particlesto have the desired jet properties for a given application. For example,the orifice can be dimensioned for high speed cutting, high precisionedge or super fine precision edge.

In the present example, the particles 34 having a carbon fibre nucleusand surrounding substance are made prior to being delivered to thehopper 40. The abrasive particles may be formed in a number of differentways, for example using sublimation, an atomiser or particles may beswirled in a super saturated liquid prior to be placed in a long dropcondensing chamber.

Referring to FIG. 5, to manufacture the particles using one exemplarymethod an atomiser 50 (e.g. an ultrasonic atomiser) may be provided. Theatomiser 50 may be connected to a mixing chamber 52. The mixing chamberis connected to a water supply 54 and a carbon fibre supply 56. Thewater supply and carbon fibre supply pass water and carbon fibre to themixing chamber, where it is mixed. The mixing chamber then supplies themixture of water and carbon fibre to the atomiser. A nitrogen supply 58is also connected to the atomiser. Once the water has been atomisedaround the carbon fibre, liquid nitrogen from the nitrogen supply isused to freeze the water around the carbon fibre. If applicable, afurther step of filtering any ice only particles from the carbon fibreand ice particles may be performed. Referring to FIG. 6, if sublimationis used to form the abrasive particles, the material to be crystallisedis heated under reduced pressure or vacuum until it vaporizes where itthen deposits on a cool area of the vessel. As the material is depositedon the cool surface, it converts into a crystalline form. A nuclei seedcan be placed at the tip of a cooled finger prior to startingsublimation allowing the crystal to form around it. For example, thematerial to be crystallised may be heated under pressure in the pressurevessel 60. A nuclei seed 62 may be provided around which the crystal canform.

In alternative embodiments, the ice and carbon fibre particles may bemade in situ within the cutting equipment. For example, referring toFIG. 4, the cutting equipment may be modified so that the hopper 40supplies carbon to a mixing chamber where it is mixed with water. Asupply of super cooled liquid can be passed around the mixing chamber asthe carbon fibres enter so as to freeze water droplets surrounding thecarbon fibre. The combined carbon fibre and ice particles are thendirected through the focus tube 44 as previously described.

In the described example, the particles are less likely to embed in thesurface of a cut component compared to the garnet particles of the priorart because of the ice surrounding the nucleus. Further, carbon fibrecan be more easily removed from the surface of a component than garnet.

Provision of a nuclei, e.g. carbon fibre nuclei, means that theparticles have increased momentum compared to particles made only fromice, which means that the cutting performance can be improved comparedto water jet cutting using only ice particles.

As discussed previously, carbon can be more easily removed from asurface than garnet. As such, advantages over the conventional garnetwater jet cutting process can be achieved by using carbon as theabrasive particle, i.e. carbon not surrounded by ice. To utilise carbononly particles a similar method to that described and illustrated inFIG. 4 may be used, but instead of the hopper containing carbon and iceparticles, the hopper contains carbon only particles. These carbonparticles may be propelled through the cartridge 40 by ultra-highpressure environmentally conditioned water feed 42A. At a certain point,e.g. puncture of a seal, a secondary encasement supply of ultra-highpressure environmentally conditioned water 42B is introduced to containand direct the impregnated cutting solution through the orifice 48 ontothe material that requires cutting.

In exemplary embodiments, the hopper may comprise a belt e.g. amulti-feed option. In examples of the described methods, the cartridge40 may be oscillated at high frequency to improve distribution of theparticles into the water stream. Cartridges are ideally disassembled andcleaned prior to replacement of media for repeated use.

In alternative examples, the nuclei may not be made from carbon fibre.For example the nuclei may be made from an acrylic. The acrylic may beproduced in a colloidal dispersion using high-shear mixing or by 3Dprinting to form particles having a desired shape, for example angularparticles with sharp edges. Selecting the desired shape of the particlescan result in more favourable abrasive particle shapes (e.g. the shapeof the acrylic nuclei and ice formed around the nuclei) for improvedcutting.

In further alternative examples the nuclei may be formed from acrystalline solid, for example uric acid crystals or crystals of otherorganic acids e.g. diprotic acids, citric acid, malic acid, tartaricacid, or folic acid. In other examples the crystals may comprisecalcium, for example calcium oxalate. The crystals may be formed fromhydroxyapatite. The crystals may be formed from urea or derivativesthereof, for example heterocyclic urea, or hydroxycarbamide. In manyexamples it is desirable for the crystals to be formed from aheterocyclic compound. In alternative examples, the crystalline solidsmay comprise metal ions. For example, calcium, magnesium, sodium,lithium, or potassium may be added to the composition of the crystallinesolids.

It will be understood that the invention is not limited to theembodiments above-described and various modifications and improvementscan be made without departing from the concepts described herein. Exceptwhere mutually exclusive, any of the features may be employed separatelyor in combination with any other features and the disclosure extends toand includes all combinations and sub-combinations of one or morefeatures described herein.

We claim:
 1. A method of manufacturing a part, the method comprising:providing a component for cutting; and directing a water jet at thecomponent so as to cut the component, the water jet comprising water andabrasive particles having a nucleus made from a first substance and asecond substance surrounding the nucleus, the first substance beingdenser than the second substance.
 2. The method according to claim 1,wherein the second substance is a liquid at atmospheric temperature andpressure.
 3. The method according to claim 1, wherein the firstsubstance is solid at atmospheric temperature and pressure.
 4. Themethod according to claim 1, wherein the second substance is ice.
 5. Themethod according to claim 1, wherein the nucleus comprises carbon. 6.The method according to claim 5, wherein the nucleus is defined by asingle carbon fibre.
 7. The method according to claim 1, wherein thenucleus comprises acrylic.
 8. The method according to claim 7, whereinthe acrylic nucleus is 3D printed prior to being surrounded by thesecond substance.
 9. The method according to claim 1, wherein the partis a fan blade for a gas turbine engine.
 10. A method of water jetcutting a component, the method comprising: providing a component forcutting; and directing a water jet at the component so as to cut thecomponent, the water jet comprising water and abrasive particles havinga nucleus made from a first substance and a second substance surroundingthe nucleus, the second substance being different to the firstsubstance.
 11. A method of manufacturing a part, the method comprising:providing a component for cutting; and directing a water jet at thecomponent so as to cut the component, the water jet comprising water andcarbon particles.